A roller brake test (RBT) is a controlled method used to measure the braking performance of heavy goods vehicles and trailers. It assesses braking force (kgf), efficiency, imbalance, binding and lock-up. These measurements allow operators to demonstrate compliance with Construction & Use Regulations and DVSA maintenance expectations.
This article reflects the updated expectations set out in the April 2025 edition of the DVSA Guide to Maintaining Roadworthiness, which strengthens requirements around brake performance assessment, the use of laden roller brake tests, and the need for documented justification when loading is impractical. All quoted material below is taken verbatim from official DVSA or legislative sources.
Under DVSA guidance, every safety inspection must include a brake performance assessment using one of three recognised methods: a laden roller brake test, EBPMS data, or a decelerometer with brake temperature readings. Laden roller brake testing remains the preferred method and is expected wherever it is practical to load the vehicle.
For full official guidance, refer to the DVSA Guide to Maintaining Roadworthiness and the DVSA brake test best practice documents cited throughout this article.
Contents
- What is a Roller Brake Test?
- Legal Requirements and DVSA Expectations
- First-Use Inspection: Operator Responsibility
- How is a Roller Brake Test Performed?
- What Does the Roller Brake Test Measure?
- Exemptions and When Risk Assessment is Required
- Why is Laden Brake Testing Important?
- Understanding Your Roller Brake Test Report
- Frequently Asked Questions
- Final Thoughts
What is a Roller Brake Test?
A roller brake test measures braking force at each wheel while the vehicle remains stationary. The rollers turn beneath the tyres, the brakes are applied gradually, and the tester records brake force, lock-up, imbalance and efficiency. Because conditions are controlled and repeatable, DVSA recognises laden roller brake testing as the most reliable and preferred method of assessing brake performance.
Legal Requirements and DVSA Expectations
Construction & Use Regulations
The legal requirement to maintain brake systems derives from Regulation 18 of The Road Vehicles (Construction and Use) Regulations 1986:
“Every part of every braking system and of the means of operation thereof fitted to a vehicle shall be maintained in good and efficient working order and be properly adjusted.”
The Road Vehicles (Construction and Use) Regulations 1986 – Regulation 18
Brake Performance at Every Safety Inspection
“Every safety inspection must assess the braking performance of the vehicle or trailer. There are 3 ways to check brake performance at a safety inspection:
1. Laden roller brake test – a recommended minimum of 3 a year as well as the MOT test
2. Decelerometer with brake temperature measurement for rigid vehicles
3. Electronic braking performance monitoring system (EBPMS) assessment.”DVSA – Maintenance investigations: questions – Braking performance
Annual Testing and Test Frequency
“You should get your HGV or trailer’s brakes tested by a roller brake tester (RBT) at least 4 times per year, including at the MOT.”
DVSA – Understanding your brake test report – Testing frequency
The April 2025 edition of the Guide to Maintaining Roadworthiness builds on these expectations by strengthening the emphasis on presenting vehicles laden for brake testing wherever practical.
First-Use Inspection: Operator Responsibility
DVSA confirms that operators—not manufacturers—are responsible for completing the first roller brake test before using a newly acquired vehicle or trailer on the road:
“Prior to using a newly acquired vehicle on the public highway, operators must conduct a first use inspection… this includes conducting a laden roller brake test when appropriate for the type of vehicle.”
DVSA – Guide to Maintaining Roadworthiness – First-use inspection
How is a Roller Brake Test Performed?
- Preparation
The vehicle is positioned on the rollers. For trailers, an external air supply may be connected. DVSA best practice expects testing at around 65% of design axle weight, unless exceptions apply. - Controlled brake application
Each axle is tested separately. The rollers rotate the wheels, brakes are applied progressively and the tester records force, imbalance, lock-up behaviour and binding. - Assessment
The system calculates brake efficiency and identifies mechanical or performance issues. Results are compared against DVSA’s HGV inspection standards.
What Does the Roller Brake Test Measure?
Brake Efficiency
For heavy vehicles, DVSA’s minimum efficiencies include:
- Service brake: ≥ 50%
- Secondary brake (where assessed separately): ≥ 25%
- Parking brake: ≥ 16%
Brake Imbalance
“The vehicle will fail if the brake imbalance is more than 30%… unless both wheels lock.”
DVSA – Understanding your brake test report – Imbalance limits
Brake Binding & Lock-Up
- Bind: residual brake force after release
- Lock-up: early wheel lock, often due to low axle loading
- Maximum brake force per wheel
Exemptions and When Risk Assessment is Required
DVSA’s brake test best practice explains that vehicles should normally be tested laden:
“Vehicles must be fully loaded before being roller-brake tested… This normally means at least 65% of the vehicle design axle weight (DAW).”
DVSA – Heavy vehicle brake test: best practice – Best practice guide
Testing unladen is only acceptable where loading is impractical due to vehicle design or the nature of the load (e.g., some tankers or livestock vehicles). In these cases operators must:
- Complete a written risk assessment explaining why laden testing is not possible
- Use an approved alternative method (EBPMS or decelerometer with brake temperatures)
- Retain all documentation for at least 15 months
The April 2025 GMTR strengthens the expectation that operators justify any deviation from laden RBT with formal documentation.
Why is Laden Brake Testing Important?
DVSA makes clear that loading is essential for valid brake testing:
“Your vehicle must be loaded for a brake test – ideally to at least 65% of its total maximum weight. It can only be tested unladen if it cannot be loaded due to design limitations or the type of load it normally carries.”
DVSA – Understanding your brake test report – Loading guidance
Laden testing provides better roller grip, reduces premature lock-up and delivers more reliable efficiency measurements.
Understanding Your Roller Brake Test Report
A typical report includes brake force (kgf), imbalance, lock-up, binding, axle weights, loading status and axle configuration. DVSA stresses the importance of correct administrative data:
“The DTp number should match the one shown on the vehicle’s plating certificate. Your test result may be incorrect if it’s wrong.”
DVSA – Understanding your brake test report – Vehicle details
Incorrect DTp details, axle weights or configuration can distort calculated efficiencies and invalidate results.
Frequently Asked Questions
Who is responsible for the first roller brake test on a new trailer?
The operator is responsible. DVSA confirms that the first-use inspection must include a laden roller brake test when appropriate for the vehicle type.
Does a trailer need to be laden for a roller brake test?
Yes. DVSA states the vehicle must be loaded—ideally to around 65% of its maximum weight—unless loading is impractical due to design or load type.
How many roller brake tests are recommended per year?
DVSA guidance advises testing at least four times per year, including the MOT, unless an EBPMS is used.
What counts as acceptable evidence of loading?
Weighbridge tickets, load calculation sheets or on-board weighing records should be retained with the brake test report.
Can a roller brake test be carried out unladen?
Only in justified cases where loading is not feasible. A written risk assessment must explain why and detail the alternative brake assessment method used.
What are common reasons for roller brake test failures?
Common causes include excessive imbalance, insufficient brake force, binding, contamination, wear and issues with adjusters.
Do tri-axle semi-trailers need special consideration?
Yes. DVSA publishes specific unladen performance tables for tri-axle semi-trailers as they can lock up prematurely when under-loaded.
What details must be correct for a valid brake test?
DTp number, axle design weights, axle configuration and recorded loading must be accurate or efficiency calculations may be unreliable.
Final Thoughts
Roller brake testing remains the most robust way to demonstrate brake performance and compliance with DVSA expectations. With the April 2025 Guide to Maintaining Roadworthiness placing increased emphasis on laden testing and documented justification where loading is impractical, operators should ensure their systems include regular laden RBTs, accurate records and correct administrative data. This supports road safety and reduces the risk of DVSA or Traffic Commissioner intervention.
